Saket Pande

A decade of Predictions in Ungauged Basins (PUB)—a review

Abstract The Prediction in Ungauged Basins (PUB) initiative of the International Association of Hydrological Sciences (IAHS), launched in 2003 and concluded by the PUB Symposium 2012 held in Delft (23–25 October 2012), set out to shift the scientific culture of hydrology towards improved scientific understanding of hydrological processes, as well as associated uncertainties and the development of models with increasing realism and predictive power. This paper reviews the work that has been done under the six science themes of the PUB Decade and outlines the challenges ahead for the hydrological sciences community. Editor D. Koutsoyiannis Citation Hrachowitz, M., Savenije, H.H.G., Blöschl, G., McDonnell, J.J., Sivapalan, M., Pomeroy, J.W., Arheimer, B., Blume, T., Clark, M.P., Ehret, U., Fenicia, F., Freer, J.E., Gelfan, A., Gupta, H.V., Hughes, D.A., Hut, R.W., Montanari, A., Pande, S., Tetzlaff, D., Troch, P.A., Uhlenbrook, S., Wagener, T., Winsemius, H.C., Woods, R.A., Zehe, E., and Cudennec, C., 2013. A decade of Predictions in Ungauged Basins (PUB)—a review. Hydrological Sciences Journal, 58 (6), 1198–1255.

Socio-hydrologic modeling to understand and mediate the competition for water between agriculture development and environmental health: Murrumbidgee River basin, Australia

Competition for water between humans and ecosystems is set to become a flash point in the coming decades in many parts of the world. An entirely new and comprehensive quantitative framework is needed to establish a holistic understanding of that competition, thereby enabling the development of effective mediation strategies. This paper presents a modeling study centered on the Murrumbidgee River basin (MRB). The MRB has witnessed a unique system dynamics over the last 100 years as a result of interactions between patterns of water management and climate driven hydrological variability. Data analysis has revealed a pendulum swing between agricultural development and restoration of environmental health and ecosystem services over different stages of basin-scale water resource development. A parsimonious, stylized, quasi-distributed coupled socio-hydrologic system model that simulates the twoway coupling between human and hydrological systems of the MRB is used to mimic and explain dominant features of the pendulum swing. The model consists of coupled nonlinear ordinary differential equations that describe the interaction between five state variables that govern the co-evolution: reservoir storage, irrigated area, human population, ecosystem health, and environmental awareness. The model simulations track the propagation of the external climatic and socio-economic drivers through this coupled, complex system to the emergence of the pendulum swing. The model results point to a competition between human “productive” and environmental “restorative” forces that underpin the pendulum swing. Both the forces are endogenous, i.e., generated by the system dynamics in response to external drivers and mediated by humans through technology change and environmental awareness, respectively. Sensitivity analysis carried out with the model further reveals that socio-hydrologic modeling can be used as a tool to explain or gain insight into observed co-evolutionary dynamics of diverse human–water coupled systems. This paper therefore contributes to the ultimate development of a generic modeling framework that can be applied to human–water coupled systems in different climatic and socio-economic settings.

Addressing diarrhea prevalence in the West African Middle Belt: social and geographic dimensions in a case study for Benin.

BackgroundIn West Africa, the Northern Sahelian zone and the coastal areas are densely populated but the Middle Belt in between is in general sparsely settled. Predictions of climate change foresee more frequent drought in the north and more frequent flooding in the coastal areas, while conditions in the Middle Belt will remain moderate. Consequently, the Middle Belt might become a major area for immigration but there may be constraining factors as well, particularly with respect to water availability. As a case study, the paper looks into the capacity of the Middle Belt zone of Benin, known as the Oueme River Basin (ORB), to reduce diarrhea prevalence. In Benin it links to the Millennium Development Goals on child mortality and environmental sustainability that are currently farthest from realization. However, diarrhea prevalence is only in part due to lack of availability of drinking water from a safe source. Social factors such as hygienic practices and poor sanitation are also at play. Furthermore, we consider these factors to possess the properties of a local public good that suffers from under provision and requires collective action, as individual actions to prevent illness are bound to fail as long as others free ride.MethodsCombining data from the Demographic Health Survey with various spatial data sets for Benin, we apply mixed effect logit regression to arrive at a spatially explicit assessment of geographical and social determinants of diarrhea prevalence. Starting from an analysis of these factors separately at national level, we identify relevant proxies at household level, estimate a function with geo-referenced independent variables and apply it to evaluate the costs and impacts of improving access to good water in the basin.ResultsFirst, the study confirms the well established stylized fact on the causes of diarrhea that a household with access to clean water and with good hygienic practices will, irrespective of other conditions, not suffer diarrhea very often. Second, our endogeneity tests show that joint estimation performs better than an instrumental variable regression. Third, our model is stable with respect to its functional form, as competing specifications could not achieve better performance in overall likelihood or significance of parameters. Fourth, it finds that the richer and better educated segments of the population suffer much less from the disease and apparently can secure safe water for their households, irrespective of where they live. Fifth, regarding geographical causes, it indicates that diarrhea prevalence varies with groundwater availability and quality across Benin. Finally, our assessment of costs and benefits reveals that improving physical access to safe water is not expensive but can only marginally improve the overall health situation of the basin, unless the necessary complementary measures are taken in the social sphere.ConclusionThe ORB provides adequate water resources to accommodate future settlers but it lacks appropriate infrastructure to deliver safe water to households. Moreover, hygienic practices are often deficient. Therefore, a multifaceted approach is needed that acknowledges the public good aspects of health situation and consequently combines collective action with investments into water sources with improved management of public wells and further educational efforts to change hygienic practices.

Weighted Bankruptcy Rules and Transboundary Water Resources Allocation

One significant problem of transboundary river basins causing various challenges and disputes throughout the world is that because of increasing water resource variability and consumption, the water demand often exceeds water availability. Hence, one of the main challenges in transboundary river basin management is how to allocate the available water among the riparian states equitably and reasonably. In this study, we propose a novel weighted bankruptcy solution method to cope with the problem of demands or “claims” exceeding resources or “assets”. Certain desirable key properties of the proposed method are provided. Furthermore, we investigate its application to the Tigris River, a shared river among Turkey, Syria and Iraq, as a real case. The available water is allocated under two different situations: homogeneous and heterogeneous group. We use the Shapley Value and compare the solution with other allocation methods applied in this study. The results suggest that this new rule may facilitate negotiation in solving conflict over the allocation of water in transboundary river basins.

Diagnosis of GLDAS LSM based aridity index and dryland identification.

The identification of dryland areas is crucial for guiding policy aimed at intervening in water-stressed areas and addressing the perennial livelihood or food insecurity of these areas. However, the prevailing aridity indices (such as UNEP aridity index) have methodological limitations that restrict their use in delineating drylands and may be insufficient for decision-making frameworks. In this study, we propose a new aridity index based on based on 3 decades of soil moisture time series by accounting for site-specific soil and vegetation that partitions precipitation into the competing demands of evaporation and runoff. Our proposed aridity index is the frequency at which the dominant soil moisture value at a location is not exceeded by the dominant soil moisture values in all of the other locations. To represent the dominant spatial template of the soil moisture conditions, we extract the first eigenfunction from the empirical orthogonal function (EOF) analysis from 3 GLDAS land surface models (LSMs): VIC, MOSAIC and NOAH at 1 1 degree spatial resolution. The EOF analysis reveals that the first eigenfunction explains 33%, 43% and 47% of the VIC, NOAH and MOSAIC models, respectively. We compare each LSM aridity indices with the UNEP aridity index, which is created based on LSM data forcings. The VIC aridity index displays a pattern most closely resembling that of UNEP, although all of the LSM-based indices accurately isolate the dominant dryland areas. The UNEP classification identifies portions of south-central Africa, southeastern United States and eastern India as drier than predicted by all of the LSMs. The NOAH and MOSAIC LSMs categorize portions of southwestern Africa as drier than the other two classifications, while all of the LSMs classify portions of central India as wetter than the UNEP classification. We compare all aridity maps with the long-term average NDVI values. Results show that vegetation cover in areas that the UNEP index classifies as drier than the other three LSMs (NDVI values are mostly greater than 0). Finally, the unsupervised clustering of global land surface based on long-term mean temperature and precipitation, soil texture and land slope reveals that areas classified as dry by the UNEP index but not by the LSMs do not have dry region characteristics. The dominant cluster for these areas has high water holding capacity. We conclude that the LSM-based aridity index may identify dryland areas more effectively than the UNEP aridity index because the former incorporates the role of vegetation and soil in the partitioning of precipitation into evaporation, runoff and infiltration. 2013 Elsevier Ltd. All rights reserved.

A Parsimonious Hydrological Model for a Data Scarce Dryland Region

Inapplicability of state of the art hydrological models due to scarce data motivates the need for a modeling approach that can be well constrained to available data and still model the dominant processes. Such an approach requires embedded model relationships to be simple and parsimonious in parameters for robust model selection. Simplicity in functional relationship is also important from water management point of view if these models are to be coupled with economic system models for meaningful policy assessment. We propose a similar approach, but rather than selecting (through calibration) processes from a set of processes predefined in terms of functionalities or modules, we model already known dominant processes in dryland areas (evaporation, Hortonian overland flows, transmission loses and subsurface flows) in a simple manner by explicitly programming them as constraints and obtain parameters by minimizing a performance based objective function. Such use of mathematical programming allows flexible model calibration and simulation in terms of available data and constraints. The model results of the approach are however not perfect given its infancy. Nonetheless its imperfections can guide us to further improvements, in particular with regards to model structure improvement.

The impact of climate change on crop production in West Africa : An assessment for the Oueme River Basin in Benin

Climate change studies for West Africa tend to predict a reduced potential for farming that will affect the food security situation of an already impoverished population. However, these studies largely ignore farmers’ adaptations and market adjustments that mitigate predicted negative effects. The paper attempts to fill some of this gap through a spatially explicit evaluation of the impact of climate change on farm income in the Oueme River Basin (ORB), Benin. The ORB is in many respects representative for the middle belt of West Africa where the predominantly sparse occupation leaves potential for migration from more densely populated areas. We apply a number of structural, spatially explicit relationships estimated for the whole territory of Benin to simulate conditions in the ORB proper that are similar to those currently prevailing in the drier North, and the more humid South. Our scenario results factor out for the main crops cultivated the constituent effects on yields, area, and revenue per ton. We find that under average climate change conditions the current low yields are not reduced, provided that cropping patterns are adjusted, while price increases partly compensate for the remaining adverse effects on farmer income. Consequently, without any policy intervention, farm incomes remain relatively stable, albeit at low levels and with increased occurrence of crop failures after extreme droughts. Scenario simulations show that there are also beneficial aspects that can, with adequate interventions, even turn losses into gains. Main channel for improvement would be the reduction of fallow, which is particularly promising because it requires few adjustments in prevailing farming practices, exploits the potential of uncultivated land and improves the water use efficiency. It also enables the Basins capacity to absorb future migrant flows from more severely affected neighboring Sahelian areas.

Hydrological model parameter dimensionality is a weak measure of prediction uncertainty

Abstract. This paper shows that instability of hydrological system representation in response to different pieces of information and associated prediction uncertainty is a function of model complexity. After demonstrating the connection between unstable model representation and model complexity, complexity is analyzed in a step by step manner. This is done measuring differences between simulations of a model under different realizations of input forcings. Algorithms are then suggested to estimate model complexity. Model complexities of the two model structures, SAC-SMA (Sacramento Soil Moisture Accounting) and its simplified version SIXPAR (Six Parameter Model), are computed on resampled input data sets from basins that span across the continental US. The model complexities for SIXPAR are estimated for various parameter ranges. It is shown that complexity of SIXPAR increases with lower storage capacity and/or higher recession coefficients. Thus it is argued that a conceptually simple model structure, such as SIXPAR, can be more complex than an intuitively more complex model structure, such as SAC-SMA for certain parameter ranges. We therefore contend that magnitudes of feasible model parameters influence the complexity of the model selection problem just as parameter dimensionality (number of parameters) does and that parameter dimensionality is an incomplete indicator of stability of hydrological model selection and prediction problems.

Land Degradation and Overgrazing in the Afar Region, Ethiopia: A Spatial Analysis

Pastoralist societies in dryland areas anticipate the harsh climatic conditions with migration patterns that optimise the use of available forage and watering points. Yet, these traditional institutions are under increasing pressure due to a mounting population, encroaching of traditional grazing areas by sedentary agriculture and restrictions on transboundary movements. Indeed, the last decades witnessed an intensified use of these rangelands and the threat of overgrazing, a major cause of land degradation, should be taken seriously. This also motivates the current study where we analyse the relationship between grazing patterns and land degradation in the nomadic pastoralist areas of the Afar Region, Ethiopia. However, this is not an easy task because trekking patterns and concentrated grazing areas are not known in sufficient detail to engage in a fully spatial-temporal analysis. Therefore, we simulate the effect of migration by analysing land degradation-overgrazing relationships under various area accessibility scenarios, gradually releasing administrative boundary restrictions for pastoralists from district zone to state level. A grazing supply to demand ratio is applied to analyse the incidence of overgrazing whereas land degradation is estimated using time series analysis of the Rainfall Use Efficiency (RUE). The study shows that fodder shortages at district level in the western Afar are partly compensated at zonal level while the demand-supply ratio at state level is close to one. Significant negative trends in RUE are found in the north-eastern part of the Afar, in isolated pockets along the Awash River and near escarpments with the Highlands. A better understanding of the land degradation-overgrazing relationship requires more information on trekking patterns, including possible visits outside the study area.

Role of Sectoral Transformation in the Evolution of Water Management Norms in Agricultural Catchments: A Sociohydrologic Modeling Analysis

This study is focused on the water-agriculture-environment nexus as it played out in the Murrumbidgee River Basin, eastern Australia, and how coevolution of society and water management actually transpired. Over 100 years of agricultural development the Murrumbidgee Basin experienced a “pendulum swing” in terms of water allocation, initially exclusively for agriculture production changing over to reallocation back to the environment. In this paper, we hypothesize that in the competition for water between economic livelihood and environmental wellbeing, economic diversification was the key to swinging community sentiment in favor of environmental protection, and triggering policy action that resulted in more water allocation to the environment. To test this hypothesis, we developed a sociohydrology model to link the dynamics of the whole economy (both agriculture and industry composed of manufacturing and services) to the communitys sensitivity toward the environment. Changing community sensitivity influenced how water was allocated and governed and how the agricultural sector grew relative to the industrial sector (composed of manufacturing and services sectors). In this way, we show that economic diversification played a key role in influencing the communitys values and preferences with respect to the environment and economic growth. Without diversification, model simulations show that the community would not have been sufficiently sensitive and willing enough to act to restore the environment, highlighting the key role of sectoral transformation in achieving the goal of sustainable agricultural development.